Numerous examples of devices of this type are known.
Such electrical supply devices are used for example to supply electrical machines of motor vehicles of the electric and/or hybrid type, i.e. which combine an electrical machine and a conventional thermal engine, for which it is important to be able to recuperate the kinetic energy in order to re-charge the vehicle battery and to supply the on-board network with electric power. This function is commonly known as recuperative braking. A battery of the metal hydride type is used, for example.
However, these electrical supply devices pose many problems.
In fact, the energy storage units undergo many cycles of charging and discharging. For example, when the motor vehicle starts, a very intense discharge of electricity occurs. Also for example, the storage units are charged with a high-intensity electric current during periods of recuperative braking.
When electric current is released during discharge operations, or when it is stored during charging operations, the ultra high-capacity storage units release more heat than conventional batteries. The quantity of heat released is proportional to the intensity of the electric current which circulates during charging or discharging.
In addition, these charging and discharging cycles can succeed one another at a very fast pace, in particular when the vehicle is travelling in town and the driver has to stop and restart the vehicle frequently.
However, in order for the storage units to be able to store the electric current efficiently, they must be kept below a maximum operating temperature.
When the charging and discharging cycles follow on from one another rapidly, the temperature of the storage units can rise very quickly to above the maximum operating temperature. The temperature increase of the storage units is all the faster since they are contained in a closed tray.
In addition, the service life of each storage unit depends on the temperature variations to which the units are exposed. Thus, according to the arrangement of each storage unit, it is common for one storage unit to be subjected to stronger temperature variations than others. This storage unit therefore has a short service life in comparison with the other storage units.
When a single storage unit is defective, it is then simpler to replace all the storage units at the same time, despite the fact that the other storage units can still function. This therefore gives rise to unnecessary expense.